Cracking oils



July 3, 1928.

cRAcRmG GILS Filed June 22, '1915- 2 Sheets-Sheet www A y 4 (ico/'gn Lfrzlcha W7 wi? www* July 3, 192s.

G. L. PRICHARD y CRACKING OILS Filed Jue 22,

1915 2 Sheets-Sheet. 2

Patented July 3, 1928.

UNITED STAT-Es PATENT OFFICE..

GEORGE L. PRIOHARD, OF PORT ARTHUR, TEXAS, AssIGEORl TO @UEE REFINING COM- PANY, OF PITTSBURGH, PENNSYLVANTA, A CORPORATION or TEXAS.

CRACKING OILS.

Application led .Tune 22, 1915. Serial No.'35,617.

This invention relates to cracking oils; and it comprises a method of cracklng Oils wherein a bodyof petroleum o1l is heated under Cracking temperature and pressure 5 while vapors of lower boiling oils are withdrawn and condensed, agitating and advantageously scouring the interior of the stlll by a device in the still operated by a shaft which passes outside of the still through a packing such as a stuffing box enclosed 1n a housing, and circulating through the housing a fluid under pressure, advantageously as great as that prevailing in, the still and advantageously of the same character as the 1 hydrocarbons being cracked in the still all as more fully hereinafter described'and asI claimed. l d

As is well known, when heavy petroleum oils, such as gas oils, petroleum residua, etc.,

are heated to a high temperature, say above 600 or 650 F., they break down with pro-` duction of lighter oils, such as kerosene Or gasoline; this being the well known cracking process. The action is facilitated by operating under pressure. The effects of pressure upon the nature of the reactlons are not well understood; it has apparently other actions than that of merely raising the boiling point of the liquid. Cracking has been performed in many types of apparatus but on a practical scale mainly in unobstructed stills externally heated. In thel cracking Operation, aside from the formation of the lighter products stated, there 1s always a deposition of carbon and this carbon is in a hard, iiinty form. It deposits on the heating elements as a coherent, dense incrustation and not only is its deposition a course of grave inconvenience and expense, since it is hard to remove from the heating elements and causes them to burn through, but it also impedes the operation by impeding the supply of heat. I have found that it also exercises another action; that lts presence has a marked influence upon the progress of the Operation. This carbon has a catalytic influence in causing the deposition of more carbon; as may be easily' perceived from the fact that newly depositing carbon invariably forms on previously deposited carbon. ing to the heating element steadily builds up, A newly formed carbon cohering to that already in existence. The net result is a hard The carbon layer coher-l dense layer covering the heating element; and where this heating element is the bottom of the still the stillbottom fills up and the plates are apt to buckle and warp.

In the ordinary operation therefore, considering a body of oil'under cracking distilto more heat, since it is next the heating element whichis hotter than the body of oil, but it is incontact with carbon which is exercisinga catalytic effect. The top of the oil body, on the other hand, is cracking under a more uniform and lower heat and substantially in the absence of carbon. Carbon does not appear to form to any great extent save next the heating element, that is, next iron, or next previously formed carbon.

I have found that in cracking oils I. can produce verymuch more uniform results and at ythe same time attain considerable economies in operation by providing stirring mechanism in the still adapted to produce a constant dissemination `of granular carbon or coke through the body of oil. In so doing not only does the stirring keep the temperature of the oil body much more uniform but I find that the coke .tends to form in small granules which do not adhere to the heating elements to such an extent as is usual. By keeping these coke granules separate and, as far as possible. uniformly distributed throughout the body Ofoil, theA newly formed carbon or coke tends to deposit on that already in existence; that is, it deposits on the granules or forms new granules. These granules being in every portion of the oil body, the cracking operation goes on much more uniformly and rapidly than is usually the case. Substantially I may say I am performing my cracking throughout the entire body of the oil, instead of, very largely, in the layers immediately in contact with the vheating elements. The stirring keeps all the .carbon formed by the presence of the catalytically acting coke granules, there is a greater tendency toward the production of saturated gasoline; something which is highly desirable.

lt is however' substantially impossible to use a stirring mechanism of any kind in the ordinary type of stills and particularly when the still is run under pressure. The walls of a still must be vapor-tight while at the same time the temperatures of oil distillaytion in the cracking operation are very high.

It is ditlicult to furnish a tight gland or a journal tor rotating` powerflriven elements of a stirrer which shall he both vapor-tight and uniform in engagement at all temperatures. ils stated, a cracking still is ordinarily run at temperatures in excess of 600 F. rll`hese ditliculties are accentuated when the still is run under pressure; say, a pressure ot 8O pounds to 300 pounds.

Il have however found that by a particular structure of the top ot the stilhl can maintain thc portion of the still body carrying the journaling means and the journaling means themselves at a lower and more convenient temperature than that prevailing in the body of the still. yAnd with these means l can produce a journaling ott the shaft which will be tight against liquid and vapor and which is not affected by the temperature of the still; in which the ournal bearing has about the same engagement with the shaft whatever the temperature of the still and of the liquid which the shaft-carried means is agitating.

ln the accompanying illustration l have shown, more or less diagrammatically, an embodiment of my invention. ln this strueture Fig. 1 is a view, partly in elevation and partly in vertical section, ot a Still under this invention;

Fig. 2 is a detailed view on an enlarged scale of the still and stirring means; and

Fig. 3 is a diagrammatical showing o-a chain stirrer.

In this showing element 1 is a still of cylindrical or other shape and made of any suitable material, such as steel boiler plate. It may be provided with external or bottom firing means 2 ot any suitable type. At its top it is provided with vapor outlet 3 leading to an air cooled chamber 4. From this chamber vapor line 5 passes to another air cooled chamber 6 beyond which is outlet 7 provided with loaded valve 8. Conduit 9 takes the vapors to diagrammatically shown condensing apparatus 10 which may be of any usual type. Beyond the condenser is a valve 11 which may be used to cause still pressure to prevail throughout the condenser. Conduit 12 leads into release chamber 13 provided with gage glasses 14 and valved gas pipe 15. This gas release pipe may lead to any suitable means for utilizing the gas (not shown). Liquid is removed from this tank through valve draw-off 16. 'lllhe air cooled condensing chambers are provided with run-back 17 communicating with bot-h and leading back into the still.

The bottom 18 of the still may be. as shown, somewhat dished. Across the still at a distance from the bottom is an angle iron bracket 19 supporting a thrust collar, 20. rll'irough this thrust collar passes vertical shaft 21 carrying cross bars 22 to which may be connected chains 23 (see lig. 3) adapted to sweep the bottom of the still. @n the top ot the still is plate 24 forming the support for the cooled bearing. @n this plate is mounted casing 25. Elements 24 and 25 may be a single casing. rllhis casing is provided with inlet 23 tor cooling duid and outlet 27. This outlet passes to cooling coil 23 in chamber 29 which may contain water or the like and thence to pump 3() which returns cooled fluid to the stated casing. At its top this casing is provided with cover plate 31. As shown, this cover plate is secured in position by bolts and is gasketed to make it removable; but it may be riveted into place. Within the casing is bearing 32 through which the shaft passes. Metallic packing 33 held in place by element 34 is provided, forming a stutling bon. rllhe cover plate carries another bearing 35 also having a good packing 36 around the shaft. At the bottom the still is provided with a draw-ott 37 for tar and granular coke. Valve 38 mounted on rod 39 servesl to control discharge of tar to the exit 40. |lhe valve rod passes through tubular casing 41 having a, screw stuliing box 42 and is operated by lever 43. Motion is given the stirrino mechanism by gears 44 from shaft 45. age 46 may be provided. Outlet 47 (see Fig. 1) may be provided leading to a safety, valve (not shown).

ln the use of this structure, the still is charged to any desired height with the oil to be cracked or distilled, such as gas oil7 petroleum residuum, heavy crude oils, etc.. 0r a. charge et ordinary crude may be placed in the still and distilled until the lighter oils are distilled. lf the pressure of the still is not desired in the condenser, valve 8 may be.

used and valve 11 left open; but if it is desired that the still pressure extend through the condenser, valve 11 may be closed to an V appropriate degree and yalve 8 kept open.'

ln either event heating is continued until gage 46 shows the desired amount ot pressure within the still. During this heating the stirrer is kept in steady movement. `When carbon begins to develop, instead of baking on the heating elements, it is formed as loose ranular material and is kept circulating tirough the body of oil. `When the desired amount of pressure is attained, valve 8 or valve 11 may be opened to the desired extent and distillation under prcssure begun. The pressure is kept at the desired point by adjustment of the firing means and of the reducing valve used., While I may use from 80 to 300 pounds pressure, I have found a pressure of about 95 pounds to be most advantageous. During this heating operation oil is kept flo-wing into the casing through inlet 26 and is discharged through outlet 27. This flow 0f oil keeps the whole bearing at a comparatively low temperature irrespective of the heat in the still. The influence of expansion being removed, a tight joint can be maintained while operating the stirrer. If desired, the oil may be introduced through 26 at a pressure equivalent to that prevailing in the still. If the oil is the same` character as that under distillation, it may even be maintained at a somewhat higher pressure so as to make leakage inward. In any event, because of the double packing means 33 and 36, leakage is not to be feared.

The stirrer may advantageously be kept going at a rate of about 3 0 revolutions per minute.

In lieu of using-oil as a cooling means in the journal sealing device 25, any" other cooling medium such a's water, glycerin, etc.,

may be used but I regard oil as being, for

many reasons, the best material.

The oil flowing through the casing 25 may be kept at any temperature desired.

When the distillation has gone to the de- 'sired extent, lever 43 may be lifted, withdrawing plug 38 and allowing the tar and coky carbon in the still to go to exit through 40. The operation of this still may be continuous, discontinuous, or semi-continuous. Where it is desired to introduce oil throughout the distillation, this may be done through inlet 48, (see Fig. 1).

What I claim is l. The process of cracking petroleum hydrocarbonswhich comprises maintaining 1n a still a body of such hydrocarbons under cracking 'temperature and pressure while withdrawing and condensing vapors of cracked products, agitating the oil bya stirring device in the still operated by a shaft passing outside the still through a packing enclosed in a closed housing and circulating through the housin a fluid under pressure.

2. The process ofg cracking petroleum hydrocarbons which comprises maintaining in a still a body of such hydrocarbons under cracking temperature and pressure while withdrawing and condensing vapors lof cracked products, agitat-ing the oil by a stirring device in the still operated by a shaft passing outside the still through a packing enclosed in a closed housing and circulating through the housing a uid under pressure' as great as that prevailing in the still.

3. The process of cracking petroleum hydrocarbons whichcomprises maintaining in a still a body of such hydrocarbons under cracking temperature and pressure while withdrawing and` condensing `vapors of cracked products, agitating the oil by a stirring device in the still operated by a shaft passing outside the still through a packing enclosed in a closed housing and circulating through the housing oil under pressure.

4. The process of cracking petroleum hydrocarbons which comprises maintaining in a still a. 'body of such hydrocarbons under cracking temperature and pressure while withdrawing and condensing vapors of cracked products, agitating the oil by a stirring device in the still operated by a shaft passing outside the still through a packing enclosed in a housing and circulating through the housing under pressure oil of the same character as that being cracked.

5. The process of cracking petroleum hydrocarbons which comprises maintaining in a still a body of such hydrocarbons under cracking temperature and pressure while r passing outside the still through a packing enclosed in a closed vhousing and circulating through the housing a Huid under pressure while supplying to the still additional hydrocarbons to be cracked.

7. The process of cracking petroleum hydrocarbons which comprises maintaining in a still a body of suchhydrocarbons under 'cracking temperature and pressure while withdrawing and condensing vapors of cracked products, agitating the oil and scouring the internal portion of the still where Carbon would'tend to deposit by device operated by a' shaft passing outside of the still through a packing enclosed in a closed housing, andcirculating through the housing a iiuid under pressure. 8..The process of cracking petroleum hydrocarbons which comprises maintaining in a still a body of such hydrocarbonsl under cracking l temperature and pressure while withdrawing and condensing vapors of cracked products, agitating the hydrocarbons in thestill by a stirring device having a shaft passing outside the still through al packing, maintainingthe packing in a closed Y chamber and controlling the temperature of the packing and the chamber by circulating through the chamber a cooling fluid under pressure.

9. The process of cracking petroleum hydrocarbons which comprises maintaining in a still a body of such hydrocarbons under cracking temperature and pressure While withdrawing and condensing vapors of cracked products, agitating the hydrocarbons in the still by a stirring device having a shaft passing outside the still through a packing, maintaining the packing in a closed chamber, controlling the temperature of the packing and the chamber by circulating through the chamber a cooling fluid under pressure, and during the circulation of such cooling liuid subjecting it to a cooling inuence outside of said Chambon 10. The process ont cracking petroleum hydrocarbons which comprises maintaining in a still a body of such hydrocarbons under cracking temperature \and pressure while withdrawing and condensing vapors of cracked products, agitating the hydrocarbons in the still by a'stiring device having a shaft passing outside the still through a packing, maintaining the packing in a closed chamber, controlling the temperature ot the packing and the chamber by circulating through the chamber a cooling oil under pressure, and during the circulation of such cooling oil subjecting it toa cooling infin-f ence outside of said chamber.

ln testimony Whereoit, l afiX my signature.

GEURGE L. PRICHARD. 

